In regards to all this stuff that you think about at night, why don't you set some time aside each week to study up on these subjects and make that the ONLY time you think about it. When you start thinking about it at night, remind yourself that you've set aside a couple hours the next day (during the day) to think about these things. Or have a couple of hours here and there where you write in a journal all the thoughts that you normally have at night. Train or condition yourself to only allow these thoughts to occur when you determine it is okay for them to occur. Maybe even something like meditating might help. Just lay on your bed for an hour or two in the afternoon and get all these thoughts out of your head.

As well, I bet if you were exhausted by bedtime, you would pass out and not have a chance to dwell on certain things. Try getting up crazy early for a few days and having a few really good workouts as well. Maybe take some Valerian root. I find two around 5pm and two more around 9pm have me totally chilled out and ready for sleep. But you have to devote yourself to it and actually want to do it.

I used to think about all that crazy stuff when I was like 7 or 8, it sucked. I would question how the world started and how it didn't make any sense, how did atoms and molecules and all the stuff just appear out of nowhere, what happened before that, was it god, is there something else we don't know about, where does the universe end, it has to end somewhere, but it can't just end, IT MAKES NO SENSE! Pretty intense thoughts to be keeping a little kid up at night. So I do feel your pain.

Good luck!